Lecture 20

Lecture 20 - Causes of Metamorphism Response of Rock...

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Unformatted text preview: Causes of Metamorphism Response of Rock Pressure Tectonic Tectonic stress stress Deform Cut by Cut Veins Veins Fluids Grow larger Grow minerals minerals Grow new Grow minerals minerals 08.08.a Temperature Processes that Cause Metamorphism Burial Subduction Heating Hot fluids Change in stress Shearing 08.09.a Observe how metamorphic conditions vary with depth Heating by magma (contact (contact metamorphism) metamorphism) Regional Regional metamorphism metamorphism Subduction-zone Subduction-zone metamorphism metamorphism 08.09.b1 Observe how cleavage relates to folds Cleavage Cleavage Fill in cleavage and beds on this hill Cleavage 08.10.b Fold and Thrust Belts Thrust faults Folds related to faults Cleavage 08.11.a Convergent Boundaries Fold and thrust belt Shearing and regional Shearing metamorphism metamorphism High T/Low P High P/Low T Mantle Part of Mantle Lithosphere Lithosphere 08.11.b Subducted Subducted Slab Slab Thrust sheets Cleavage and Cleavage shear zones shear Regional metamorphism Regional Regional metamorphism metamorphism Rift Divergent Boundaries Metamorphism Metamorphism by hot seawater by Seawater Oceanic Oceanic Crust Crust Contact Contact metamorphism metamorphism Asthenosphere Mid-ocean ridge 08.12.a Continental rift Rift Rift g readin p floor s Sea Normal Normal faults faults Metamorphism Asthenosphe re Metamorphism ere nosph Asthe Normal Faults and Tilting of Fault Blocks 08.12.c Above larger normal fault Observe these features Observe along fault zones along 08.13.a Scratch marks Drag folds Fault breccia Observe these features along shear zones Shearing Deformation Melted rock 08.13.b Strike-Slip Faults and Shear Zones Shear stress Shearing moves rocks 08.13.c Shear within Shear plates plates Transform faults Observe joints in the landscape 08.14.a Vertical joints Weathering and joints Joint sets Columnar joints Observe tilted and folded layers in the landscape Dip slope 08.14.b Flatirons Ho gb ac k Observe how faults are expressed in the landscape 08.14.c Fault truncates layers Fault scarp Fault zone forms notch Active fault Active offsets stream channels channels Observe metamorphic rocks in the landscape 08.14.d Shiny Folded schist Contorted Contorted and platy and What are some ways we could study geologic structures? Record observations Map rocks and Map structures structures Look for Look evidence evidence 08.15.a Measure Measure orientation of features features Observe this geologic map of New England Thick lines are faults Metamorphic rocks Metamorphic shown stippled shown Precambrian: Precambrian: brown, olive green brown, Paleozoic: pink, purple, blue Mesozoic: bluegreen, orange 08.16.a Observe structures and metamorphic Observe conditions across New England conditions Temperature Temperature and pressure history history 08.16.b Investigation: Observe Structural and Metamorphic Investigation: Events that Occurred Here Events Blocks show dip Tan and gray Tan bedding bedding Cleavage forms Cleavage notches notches Sketch from Sketch southern hill southern 34 5 Stream flows Stream along a notch along Banded rocks Banded with steep metamorphic layers layers Samples Samples collected from sites 1-4; observations made at site 5 made 08.17.a 2 1 ...
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